I just picked up my first rifle, a Mosin 91/59 yesterday.  I put about 20 rounds through it and it was a blast to shoot!  My father-in-law is an FFL so he gave me a cleaning kit with a 7.62/.30cal brush.  It seemed very hard to push through the bore.  Is that normal?  I don't want to do any damage as it seems like it's in great shape.  Also, since I have corrosive ammo, I dumped some water down the barrel, used the brush, then a patch soaked in lube.  I also rinsed the bolt off and cleaned and lubed that as well.  Should that be sufficient?

.30 cal is what you need.  I use only 9mm brushes for my 7.62mm rifles and 9mm pistols........keeps things simple.

The 30 cal brush will work, but it will wear out quickly and become loose fitting in the bore. I use a worn down 8mm (.323) brush in my Mosins. Then when it wears down some I use them in a standard .308 bore.
Hoppes #9 will work with corrosive ammo also.

Alright, so it sounds like going even bigger isnt an issue.  I did also just get an XD9 so I'll need to grab a 9mm brush as well.  If I can use that for both that would be great.

I've found that .357 pistol (brass) brushes work very well.

I do the same thing.